Messages in this thread | | | Date | Fri, 19 Nov 2010 08:12:18 +0800 | From | Shaohui Zheng <> | Subject | Re: [1/8,v3] NUMA Hotplug Emulator: add function to hide memory region via e820 table. |
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On Thu, Nov 18, 2010 at 01:16:07PM -0800, David Rientjes wrote: > On Thu, 18 Nov 2010, Shaohui Zheng wrote: > > > > > Index: linux-hpe4/arch/x86/kernel/e820.c > > > > =================================================================== > > > > --- linux-hpe4.orig/arch/x86/kernel/e820.c 2010-11-15 17:13:02.483461667 +0800 > > > > +++ linux-hpe4/arch/x86/kernel/e820.c 2010-11-15 17:13:07.083461581 +0800 > > > > @@ -971,6 +971,7 @@ > > > > } > > > > > > > > static int userdef __initdata; > > > > +static u64 max_mem_size __initdata = ULLONG_MAX; > > > > > > > > /* "mem=nopentium" disables the 4MB page tables. */ > > > > static int __init parse_memopt(char *p) > > > > @@ -989,12 +990,28 @@ > > > > > > > > userdef = 1; > > > > mem_size = memparse(p, &p); > > > > - e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1); > > > > + e820_remove_range(mem_size, max_mem_size - mem_size, E820_RAM, 1); > > > > + max_mem_size = mem_size; > > > > > > > > return 0; > > > > } > > > > > > This needs memmap= support as well, right? > > we did not do the testing after combine both memmap and numa=hide paramter, > > I think that the result should similar with mem=XX, they both remove a memory > > region from the e820 table. > > > > You've modified the parser for mem= but not memmap= so the change needs > additional support for the latter. >
the parser for mem= is not modified, the changed parser is numa=, I add a addtional option numa=hide=.
From current discussion, numa=hide= interface should be removed, we will use mem= to hide memory.
> > > > early_param("mem", parse_memopt); > > > > > > > > +#ifdef CONFIG_NODE_HOTPLUG_EMU > > > > +u64 __init e820_hide_mem(u64 mem_size) > > > > +{ > > > > + u64 start, end_pfn; > > > > + > > > > + userdef = 1; > > > > + end_pfn = e820_end_of_ram_pfn(); > > > > + start = (end_pfn << PAGE_SHIFT) - mem_size; > > > > + e820_remove_range(start, max_mem_size - start, E820_RAM, 1); > > > > + max_mem_size = start; > > > > + > > > > + return start; > > > > +} > > > > +#endif > > > > > > This doesn't have any sanity checking for whether e820_remove_range() will > > > leave any significant amount of memory behind so the kernel will even boot > > > (probably should have a guaranteed FAKE_NODE_MIN_SIZE left behind?). > > > > it should not be checked here, it should be checked by the function who call > > e820_hide_mem, and truncate the mem_size with FAKE_NODE_MIN_SIZE. > > > > Your patchset doesn't do that, I'm talking specifically about the amount > of memory left behind so that the kernel at least still boots. That seems > to be a function of e820_hide_mem() to do some sanity checking so we > actually still get a kernel rather than the responsibility of the > command-line parser.
How much memory is enough to make sure the kernel can still boot, it is very hard to measure. it is almost impossible to get the exact data. I try to leave very few memory to kernel(hide most memory with numa=hide), it cause a panic directly.
I have no idea about it, do you have any suggestions?
Another example, I try to add paramter "mem=1M", it compains "Select item can not fit into memory", and I did not find where the error message comes from, I guess that it should be printed by grub.
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